The complexity of the large airport platforms associated with considerable and rapidly growing traffic, is making the taxiing phase into an increasingly tricky phase for pilots notably when they have limited experience of this airport and its constraints. The pilot must manoeuvre the aeroplane along a pathway comprising numerous intersections whilst monitoring the traffic, while complying with the controller's taxi authorizations, usually called clearances, and while making preparations for takeoff. This may lead to errors of assessment, and the aeroplane may be in zones where it is not authorized, entailing risks of collisions.
In modern aircraft, to ensure the airport navigation function, two types of systems exist for aiding traffic flow on the ground. These are:                A navigation aid system allowing the pilot, on the one hand, to ascertain the position of the aircraft in the airport at any moment, on the other hand, to indicate to him which path to follow to get from one point to another on the airport. Generally the useful information is exhibited on a so-called head-down instrument panel display. This information comprises: a mobile electronic map of the airport, the position of the aircraft on the manoeuvring area of the airport, the taxi pathway to be followed and the stop points, the latter correspond to the taxi authorizations provided by ground control.        A taxi aid system allowing the pilot to follow, as closely as possible, the preset trajectory coming from control. In the latter case, useful information is presented on a head-up collimator also called an HUD, the acronym standing for Head-Up Display. A head-up collimator conventionally comprises a source of images generating a symbology, collimation optics and an optical combiner placed in the pilot's visual field. The collimator thus gives an image at infinity of the symbology overlaid on the outside landscape. The taxi aid can also be displayed on the head-down displays.        
The symbology gives information on the trajectory to be followed and a certain number of presets. It is generated by a computer dedicated to the collimator. In the case of the system for aiding taxiing, the information is provided to the computer of the collimator by:
The main navigation system, notably in respect of the information regarding heading, speed over the ground and position for example.
The airport navigation computer providing the preset data originating from the taxi pathway.
Currently, within the framework of the airport phases, the distribution of the on-board/ground control responsibilities, the operational procedures, the density of the traffic and the considerable number of parties on the airport platform do not enable an aircraft to employ equipment having the capacity to assimilate all the information in order to move in an optimal manner.
The construction of the “taxi plan” is heavily imposed by the ground control authority or “ATC”, the acronym standing for the expression Air Traffic Control and is often incremental and partial as a function of the various control zones distributed over the airport. For example, on international airports of large expanse, such as Paris Charles De Gaulle, one controller is in charge of the zone of the runways, a second in an airport zone (e.g.: South West part) of the taxiways and a third in another zone possibly being a platform manager. The pathway is then dictated to the pilot as he advances. He stops at the limits of each control zone and cannot travel the whole way, from the runway to the boarding gate (or the reverse journey).
The problem with the construction of the taxi plan is that it may then be erroneous or that it may lack information, notably stop points to wait for authorizations.
Airport mapping systems exist, such as for example those present in EFBs, the acronym standing for Electronic Flight Bag, OANS, On Board Airport Navigation System, a device specific to the Airbus aircraft manufacturer. These systems make it possible:                To display the map of the airport showing the position of the aircraft and its situation with respect to the topology of the airport and to the surrounding structures,        To obtain information on “airport items” by way of the user interface,        To obtain annotations, advice (e.g. “Approaching Runway”).But these functions ensure only limited monitoring, relying as they do exclusively on databases describing the geometry of the airport with respect to the current position of the aeroplane, and not to the rules of use dictated (and modified periodically) by the local control authorities and specifically established over the pathway envisaged by the aeroplane.        
Finally certain functions, such as the “RAAS”, the acronym standing for the expression Runway Awareness and Advisory System from Honeywell, available through the product EGPWS, have the role of warning the crew when approaching a runway. They are based on the sole information about the runways, independently of the possible connections to the taxiways or of their actual activity. Moreover, the segregation of the equipment used during the taxiing phases, prevents these messages from being correlated with pathway information formulated through a routing means or a richer database having all the information about the airport surface.
U.S. Pat. No. 6,694,249 from Rockwell Collins is also known. This document deals with the aspect regarding display of the airport map, clearances and calculation of the suitable speed, but does not tackle pathway monitoring and clearances monitoring.